This invention concerns cationic latex terpolymer flocculants and their use for waste water treatment.
It is well known that the clarification or dewatering of sewage and industrial sludges and similar organic suspensions may be aided by chemical reagents, added in order to induce a state of coagulation or flocculation which facilitates the process of solid/liquid or liquid/liquid separation from water. For this purpose, lime or salts of iron or aluminum have been utilized. More recently synthetic polyelectrolytes, particularly certain cationic latex flocculants such as copolymers of acrylamide and dimethylaminoethylacrylate, have been found to be of interest.
These types of polymers are broadly termed coagulants and flocculants. These polymers can be utilized in such diverse processes as emulsion breaking, sludge dewatering, raw water clarification, drainage and retention aids in the manufacture of pulp and paper, flotation aids in mining processing and color removal.
In the water treatment field of solids/liquid separation, suspended solids are removed from water by a variety of processes, including sedimentation, straining, flotation, filtration, coagulation, flocculation, and emulsion breaking among others. Additionally, after suspended solids are removed from the water they must often be dewatered so that they may be further treated or properly disposed of Liquids treated for solids removal often have as little as several parts per billion of suspended solids or dispersed oils, or may contain large amounts of suspended solids or oils. Solids being dewatered may contain anywhere from 0.25 weight percent solids, to 40 or 50 weight percent solids material. Solids/liquid or liquid/liquid separation processes are designed to remove solids from liquids, or liquids from liquids.
While strictly mechanical means have been used to effect solids/liquid separation, modern methods often rely on mechanical separation techniques that are augmented by synthetic and natural polymeric materials to accelerate the rate at which solids can be removed from water. These processes include the treatment of raw water with cationic coagulant polymers that settle suspended inorganic particulates and make the water usable for industrial or municipal purposes. Other examples of these processes include the removal of colored soluble species from paper mill effluent wastes, the use of organic flocculant polymers to flocculate industrial and municipal waste materials, sludge recovery and emulsion breaking.
A benchmark test for evaluating the effectiveness of a flocculant is the so-called drainage test in which the polymer is added to sludge and mixed so that the polymer flocculates the sludge. The mixture is then poured through a belt filter press cloth and the rate at which water drains is taken as a measure of polymer performance.
Regarding the mechanism of separation processes, particles in nature have either a cationic or anionic charge. Accordingly, these particles often are removed by a water-soluble coagulant or flocculent polymer having a charge opposite to that of the particles. This is referred to as a polyelectrolyte enhanced solids/liquid separation process, wherein a water-soluble or dispersible ionically charged polymer is added to neutralize the charged particles or emulsion droplets to be separated. The dosage of these polymers is critical to the performance of the process. Too little ionically charged polymer, and the suspended particles will not be charge neutralized and will thus still repel each other. Too much polymer, and the polymer will be wasted, or worse, present a problem in and of itself.
Notwithstanding the variety of commercially available polymers that have been found to be capable of flocculating or coagulating solids sludges, there are various circumstances which tend to limit the usefulness of these reagents. While for certain sludges economical treatments with these known reagents are feasible, more often sludges require very high and cost-ineffective dosages of reagents for successful treatment. Moreover, variations often occur in sludge from any one source. For example, variations in the supply of material to the waste water/sludge/paper furnish process water and/or in the oxidizing conditions that may be involved in the production of these waters lead to a variety of particle types which must be removed. Furthermore, it is not uncommon to encounter sludges that are, for some reason, not amenable to flocculation by any of the known polymeric flocculating agents.
Therefore, there is a need for an improved family of polymers that provide better drainage at lower doses than the currently-available acrylamide/dimethylaminoethylacrylate copolymers.
We have discovered new cationic terpolymers which are 15 to 20 percent more efficient than currently-available acrylamide/dimethylaminoethylacrylate copolymers.
Accordingly, in its principle aspect, this invention is directed to a cationic terpolymer comprising
(a) a first monomer unit selected from acrylamide and methacrylamide;
(b) a second monomer unit selected from dimethylaminoethyl acrylate methyl chloride quaternary salt, 3-(acrylamido)propyltrimethylammonium chloride, 3-(methacrylamido)propyltrimethylammonium chloride, dimethylaminoethyl methacrylate methyl chloride quaternary salt, dimethylaminoethyl acrylate dimethylsulfate quaternary salt, dimethylaminoethyl methacrylate dimethylsulfate quaternary salt, diethylaminoethyl acrylate methyl chloride quaternary salt and diethylaminoethyl acrylate dimethylsulfate quaternary salt; and
(c) a third monomer unit selected from benzyl methacrylate, 2,2,2-trifluoroethyl acrylate, acrylamide diacetone, N-phenylacrylamide, 2,2,3,3-tetrafluoropropyl acrylate and poly(propylene glycol)methacrylate.
Definitions of Terms
As used herein, the following abbreviations and terms shall have the following meanings:
xe2x80x9cADAxe2x80x9d means diacetone acrylamide, available from Chemie Linz U.S. Inc., Fort Lee, N.J.
xe2x80x9cAlfonic(copyright)1412-60xe2x80x9d is a ethoxylated linear alcohol (60% ethylene oxide), available from Vista Chemical Co., Houston, Tex.
xe2x80x9cAMxe2x80x9d for acrylamide.
xe2x80x9cAIBNxe2x80x9d for 2,2xe2x80x2-azobis(isobutyronitrile), available from E.I. duPont Nemours and Co. Inc.; Wilmington, Del.
xe2x80x9cAIVNxe2x80x9d for 2,2xe2x80x2-azobis(2,4-dimethylvaleronitrile), available from E.I. duPont Nemours and Co. Inc.; Wilmington, Del.
xe2x80x9cDMAEAxe2x80x9d for dimethylaminoethyl acrylate.
xe2x80x9cDMAEMxe2x80x9d for dimethylaminoethyl methacrylate.
xe2x80x9cDMAEA.MCQxe2x80x9d for dimethylaminoethyl acrylate, methyl chloride quaternary salt.
xe2x80x9cEDTA.4Na+xe2x80x9d for ethylenediaminetetraacetic acid, tetrasodium salt.
xe2x80x9cNaClxe2x80x9d for sodium chloride.
xe2x80x9cNaNO3xe2x80x9d for sodium nitrate.
xe2x80x9cPOExe2x80x9d for polyoxyethylene.
xe2x80x9cPPGxe2x80x9d for poly(propylene glycol).
xe2x80x9cSpan 80xe2x80x9d for sorbitan monooleate from ICI Specialty Chemicals, Wilmington, Del.
xe2x80x9cTriton(copyright)N-101xe2x80x9d for Nonylphenoxy polyethoxy ethanol, available from Rohm and Haas Co., Philadelphia, Pa.
xe2x80x9cTween 61xe2x80x9d for POE (4) sorbitan monostearate, available from ICI Specialty Chemicals, Wilmington, Del.
xe2x80x9c1H-NMRxe2x80x9d for Proton Nuclear Magnetic Resonance Spectroscopy.
xe2x80x9crpmxe2x80x9d for revolutions-per-minute.
xe2x80x9cChain Transfer Agentxe2x80x99 means any molecule, used in free-radical polymerization, which will react with a polymer radical forming a dead polymer and a new radical. Representative Chain Transfer Agents are listed by K. C. Berger and G. Brandrup, xe2x80x9cTransfer Constants to Monomer, Polymer, Catalyst, Solvent, and Additive in Free Radical Polymerization, xe2x80x9d Section II, pp. 81-151, in xe2x80x9cPolymer Handbook, xe2x80x9d edited by J. Brandrup and E. H. Immergut, 3d edition, 1989, John Wiley and Sons, New York.
xe2x80x9cInverse emulsion polymerxe2x80x9d and xe2x80x9cinverse latex polymerxe2x80x9d mean a water-in-oil polymer emulsion comprising a cationic terpolymer according to this invention in the aqueous phase, a hydrocarbon oil for the oil phase and a water-in-oil emulsifying agent. Inverse emulsion polymers are hydrocarbon continuous with the water-soluble polymers dispersed within the hydrocarbon matrix. The inverse emulsion polymers are then xe2x80x9cinvertedxe2x80x9d or activated for use by releasing the polymer from the particles using shear, dilution, and, generally, another surfactant. See U.S. Pat. No. 3,734,873, incorporated herein by reference.
Inverse emulsion polymers are prepared by dissolving the required monomers in the water phase, dissolving the emulsifying agent in the oil phase, emulsifying the water phase in the oil phase to prepare a water-in-oil emulsion, homogenizing the water-in-oil emulsion and polymerizing the monomers to obtain the polymer. A self-inverting surfactant may be added to the water-soluble polymer dispersed within the hydrocarbon matrix to obtain a self-inverting water-in-oil emulsion. Alternatively, a polymer solution can be made-up by inverting the polymer dispersed in oil in to water containing the surfactant.
xe2x80x9cRSVxe2x80x9d stands for Reduced Specific Viscosity. Within a series of polymer homologs which are substantially linear and well solvated, xe2x80x9creduced specific viscosity (RSV)xe2x80x9d measurements for dilute polymer solutions are an indication of polymer chain length and average molecular weight according to Paul J. Flory, in xe2x80x9cPrinciples of Polymer Chemistryxe2x80x9d, Cornell University Press, Ithaca, N.Y.,(copyright) 1953, Chapter VII, xe2x80x9cDetermination of Molecular Weightsxe2x80x9d, pp.266-316. The RSV is measured at a given polymer concentration and temperature and calculated as follows:       RSV    =                  [                              (                          η              /                              η                o                                      )                    -          1                ]            c            η    =          viscosity      ⁢              xe2x80x83            ⁢      of      ⁢              xe2x80x83            ⁢      polymer      ⁢              xe2x80x83            ⁢      solution                  η      o        =          viscosity      ⁢              xe2x80x83            ⁢      of      ⁢              xe2x80x83            ⁢      solvent      ⁢              xe2x80x83            ⁢      at      ⁢              xe2x80x83            ⁢      the      ⁢              xe2x80x83            ⁢      same      ⁢              xe2x80x83            ⁢      temperature            c    =          concentration      ⁢              xe2x80x83            ⁢      of      ⁢              xe2x80x83            ⁢      polymer      ⁢              xe2x80x83            ⁢      in      ⁢              xe2x80x83            ⁢              solution        .            
The units of concentration xe2x80x9ccxe2x80x9d are (grams/100 ml or g/deciliter). Therefore, the units of RSV are dl/g. In this patent application, for measuring RSV, the solvent used is 1.0 molar sodium nitrate solution. The polymer concentration in this solvent is 0.045 g/dl. The RSV is measured at 30xc2x0 C. The viscosities xcex7 and xcex70 are measured using a Cannon Ubbelohde semimicro dilution viscometer, size 75. The viscometer is mounted in a perfectly vertical position in a constant temperature bath adjusted to 30xc2x10.02xc2x0 C. The error inherent in the calculation of RSV is about 2 dl/grams. When two polymer homologs within a series have similar RSV""s that is an indication that they have similar molecular weights.
xe2x80x9cBased on polymer activexe2x80x9d and xe2x80x9cbased on monomerxe2x80x9d mean the amount of a reagent added based on the level of vinylic monomer in the formula, or the level of polymer formed after polymerization, assuming 100% conversion.
xe2x80x9cBased on formulaxe2x80x9d means the amount of reagent added based on the total formula weight.